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Yuki
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Reverse incremntal - if failed - how is it handled?

Post by Yuki » Apr 08, 2011 6:30 pm

Question 1
Since reverse incremntals always creates a FULL backup by injecting changed blocks and creating an incremental file with "old-changed" blocks. If during the FULL injection a disaster happens. Can Veeam software recover from that? Does it roll-back the incomplete changes to restore the "previous-FULL" ?

Example:
Schema used - Reverse incremental
Schedule: Daily

Monday - first backup (FULL)
Tuesday - first reverse incremental ( Monday is turned into incremental, Tuesday is now FULL)
Wednesday - second reverse incremental ( Tuesday is now turned into incremental, Wednesday is FULL) - during the injection something happens and the only surviving piece of equipment is the backup device. Wednesday's backup did not finish mangling the files.

Is the entire backup chain unusable?

Question 2
Let's say we have an entire week of Reverse Incremental backups (Monday-Sunday). If we need to restore Thursday - will Veeam software need Sunday+Saturday+Friday+Thursday or will it need Sunday+Thursday?
If it is the later - that means that during a reverse incremental EVERY incremental file is modified every time a backup is created?
So when Sunday reverse incremental creates the full backup - it also updates every incremental in the entire chain?

Example:
Schema used - Reverse incremental
Schedule: Daily

Monday - first backup (FULL)
Tuesday - first reverse incremental ( Monday is turned into incremental, Tuesday is now FULL)
Wednesday - second reverse incremental ( Tuesday is now turned into incremental, Wednesday is FULL).
We need to restore Monday, but find out that Tuesday incremental is corrupt or missing - I assume we can't restore?


I'm just trying to understand how this work - if it is a truly incremental type or more of "reverse-differential"

Gostev
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Re: Reverse incremntal - if failed - how is it handled?

Post by Gostev » Apr 08, 2011 6:35 pm

Q1. Yes, we simply restore VBK to last known good state before attempting another incremental pass. But you can restore from any previous successful restore point even before this happens.

Q2. It is truly incremental type. You need latest backup (VBK file), and uninterrupted chain of reversed increments (VRB files) going from said VBK to your required restore point.

Thanks.

Yuki
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Re: Reverse incremntal - if failed - how is it handled?

Post by Yuki » Apr 08, 2011 6:43 pm

So in reverse incremental, every incremental file is updated every time backup runs?

Gostev
SVP, Product Management
Posts: 24416
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Re: Reverse incremntal - if failed - how is it handled?

Post by Gostev » Apr 08, 2011 6:52 pm

Yuki, honestly, you should finally read that sticky FAQ topic. :D

Yuki
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Re: Reverse incremntal - if failed - how is it handled?

Post by Yuki » Apr 08, 2011 7:24 pm

Gostev, honestly, i did :)

Gostev
SVP, Product Management
Posts: 24416
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Re: Reverse incremntal - if failed - how is it handled?

Post by Gostev » Apr 08, 2011 7:25 pm

Thank you :D

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